Background Electrical injuries, although relatively uncommon, are inevitably encountered by most emergency physicians. Adult electrical injuries usually occur in an occupational setting, whereas children are primarily injured in the household setting. The spectrum of electrical injury is very broad, ranging from minimal injury to severe multiorgan involvement, with both occult and delayed complications, to death.Presentation Electrical injuries can present with a variety of problems, including cardiac or respiratory arrest, coma, blunt trauma, and severe burns of several types. It is important to establish the type of exposure (high or low voltage), duration of contact, and falls or other trauma.
outline• Physics of injury• Mechanisms of Injury• Associated Injuries• Management• Prognosis
Physics of injuryElectro thermal Heating Formulas • P = (IxI)Rt and ( I=V/R) • P thermal power (heat), in Joules • I current, in amperes • R resistance, in ohms • t time, in seconds • V potential, in volts
Factors Determining Electrical Injury • Type of circuit • Resistance of tissues • Amperage • Duration • Voltage • Pathway of current
Type of Circuit: • One of the factors affecting the nature and severity of electrical injury is the type of circuit involved, either direct current (DC) or alternating current (AC). • High-voltage DC contact tends to cause a single muscle spasm, often throwing the victim from the source. This results in a shorter duration of exposure but increases the likelihood of traumatic blunt injury. Brief contact with a DC source can also result in disturbances in cardiac rhythm, depending on the phase of the cardiac cycle affected,
• AC exposure to the same voltage tends to be three times more dangerous than DC. Continuous muscle contraction, or tetany, can occur when the muscle fibers are stimulated at between 40 and 110 times per second.
Resistance• Resistance is the tendency of a material to resist the flow of electric current; it is specific for a given tissue, depending on its moisture content, temperature, and other physical properties.• The higher the resistance of a tissue to the flow of current, the greater the potential for transformation of electrical energy to thermal energy.• Nerves, muscle and blood vessels, because of their high electrolyte and water content, have a low resistance and are good conductors.• Bone, tendon, and fat, which all contain a large amount of inert matrix, have a very high resistance and tend to heat up and coagulate rather than transmit current.• The other tissues of the body are intermediate in resistance (eg dry skin)
Current ( Amperage ) Current, expressed in amperes, is a measure of the amountof energy that flows through an object. • Amperage is dependent on the source voltage and the resistance of the conductor. (Remember I=V/R) • The voltage of the source is known but the resistance varies • The physical effect vary with different amperage. "let go" current • the maximum current at which a person can grasp the current and then release it before muscle tetany makes letting go impossible.
Duration of contact• The longer the duration of contact with high-voltage current, the greater the electro thermal heating and degree of tissue destruction.With lightening injury• The extremely short duration and extraordinarily high voltage and amperage of lightning both result in a very short flow of current internally, with little, if any, skin breakdown and almost immediate flashover of current around the body.
VoltageVoltage is a measure of the difference in electricalpotential between two points and is determined by theelectrical source. Electrical injuries are conventionallydivided into high or low voltage using 500 or 1000 V asthe most common cutpoint.The higher the voltage the more is tissue distractionNo fatalities with low voltage
PathwayThe pathway that a current takes determines the tissues at risk, thetype of injury seen, and the degree of conversion of electrical energy toheat. This is true whether high, low, or lightning voltages are beingconsidered.Current passing through the heart or thorax can cause cardiacdysrhythmias and direct myocardial damage. Current passing throughthe brain can result in respiratory arrest, seizures, and paralysis.Current in proximity to the eyes can cause cataracts
Mechanism of injury1. Electrical Injury2. Lightning InjuryElectrical Injury• The primary electrical injury is burns. Secondary blunt trauma results from falls or being thrown from the electrical source by an intense contraction of muscles. Electrical burns can be classified into four different types.
Types of Electrical Burns• Direct contact 1. Electrothermal heating • Low voltage :limited to the affected area • High voltage : burn any where along the current path• Indirect contact1. Arc: An electrical arc is a current spark formed between two objects of differing potential that are not in contact with each other, usually a highly charge source and a ground. Because the temperature of an electrical arc is approximately 2500° C, it is most destructive indirect injury. It causes very deep thermal burns at the point where it contacts the skin. In arcing circumstances, burns may be caused by the heat of the arc itself, electrothermal heating due to current flow, or by flames that result from the ignition of clothing.2. Flame: Ignition of clothing causes direct burns from flames.3. Flash: When heat from a nearby electrical arc causes thermal burns but current does not actually enter the body
Lightning Injury• Lightning injury may occur by five mechanisms .• Direct strike• Orifice entry: It has been substantiated experimentally that lightning strikes near the head may enter orifices such as the eyes, ears, and mouth to flow internally.This may help explain the eye and ear symptoms and signs that are reported with lightning injury.• Contact1. Side flash, “splash”: Side flash or splash occurs as lightning jumps from its primary strike object to a nearby person on its way to ground2. Ground current or step voltage: Step voltage, a difference in electrical potential between a person’s feet, may occur as lightning current spreads radially through the ground. A person is a far better conductor of electricity than the earth.• Blunt trauma: Blunt injury from lightning can occur from two mechanisms. First, the person may be thrown a considerable distance by the sudden, massive contraction caused by current passing through the body. Second, an explosive or implosive force of lightning.
Associated Injuries Respiratory System Suffocation secondary to tetanic muscle contractions Respiratory arrest secondary to direct injury .Cardiovascular System Asystole (more likely if DC or high V) Arrhythmias (more likely AC) (~15% pts) Ventricular fibrillation most common fatal arrhythmia Myocardial necrosis (thermal effect) Anoxic injury secondary to respiratory arrestNeurological System Direct effects include LOC, autonomic dysfunction, amnesia, tempparalysis (keraunoparalysis ( (clear within hours)) Spinal Cord injury secondary to spine fracture secondary to musclecontractions Peripheral motor/sensory losses (long-term sequel)
Associated InjuriesSkin(~57% low V fatalities; ~96% high V fatalities)*Superficial, partial or full thickness thermal burnsDegree of external injury can underestimate internal injury & vice-versa. Oneshould not attempt to predict the amountof underlying tissue damage from theamount of cutaneous involvementMuscleNecrosis secondary to severe contraction or thermal injuryCompartment syndrome secondary to edema from deep injury & 3rd spacingSkeletalOsteonecrosis secondary to thermal injuryFracture secondary to muscle contraction or blunt trauma
Associated InjuriesRenalPigment-induced renal failureHypovolemia secondary to 3rd spacing can lead to prerenalGIInjury rare, most commonly “Curler’s ulcers”( ulcer from burn)Head, Eye and ENTCataracts can develop up to 2 years afterHearing loss from 8th nerve injuryDamage to any organ system secondary to blunt traumaDamage to any organ system secondary to vascular damage
Management Securing the scene • Power source should be turned off • Use of electrical gloves by medical personnale is dangerous • Denergizing the lines • Triage should be concentrated on the presence of cardiac or respiratory arrest • Patients require cardiac & trauma care
ManagementStandard ABCDEs of any major traumaPulmonary Low threshold for intubation, as respiratory failure commonCardiac Serial monitoring if high V, abnormal ECG, LOC, respiratory arrest, or PMH of CV dysfunctionNeuro C-spine and log-roll precautions; CT head & spine often warranted Thorough serial neurological exams, as vessel coagulation can result in late sequel
ManagementMusculoskeletal – Thorough evaluation for fractures – Serial evaluations of limbs for compartment syndrome requiring emergent decompression – Even in absence of compartment syndrome, persistent aciduria or myoglobinuria may require limb amputationSkin – Early debridement and later reconstruction – Antibiotic prophylaxis (controversial)
Management Renal – Fluid resuscitation key, as 3rd spacing common & myoglobinuria secondary to rhabdomyolysis can cause ARF Specific therapy Rhabdomyalisis (damaging of skeletal muscle tissue) • Urinary alkalinization • Mannitol & frusamide • Urine output maintained at 1-1.5 ml/kg/hr • Ph of blood maintained at 7.4 by sodium carbonate GI – Ulcer prophylaxis, as gastric ulcers (Curling’s ulcers) can develop – Ileus uncommon, but should prompt evaluation for other injury • Serial evaluation of liver, pancreatic, & renal function for traumatic/anoxic/ischemic injury • Careful management of fluid and electrolytes to avoid acidosis and compartment syndromes
All patients require : ECG Cardiac enzymes CT scan for victims with altered mental status or detororation of neurologicalstatusLaboratory : CBC , Ur ,Cr, Na, K, urinalysis Liver & pancreatic enzymes , coagulation if there is abdominal trauma CK level ( predict muscle injury) Radiological study according to the injured area
PrognosisHighly variable, depending on severity of both initial injury and subsequentcomplicationsHigh morbidity/mortality in patients with multisystem organ failureAdvances in surgical interventions (early excision, fasciotomy, skin grafts, etc…)have improved prognosis.
Arcing electrical burns through the shoe around the rubber sole